Poration



Patented Aug. 28, 1928.

' UNITED STATES PATENT OFFICE.

WALTER A. PATRICK, 0F BALTIMORE, MARYLAND, ASSIGNOR TO THE SILICA GELCOR- PORATION, OF BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND.

METHOD OF MAKING ALUMINUM-OXIDE GELS.

No Drawing. Original application filed February 18, 1921, Serial No.446,108. Divided and this application filed May 24, 1924. Serial No.715,729.

The present application which is a division of my application 446,108filed February 18, 1921, relates to a method of making an adsorbent andcatalytic gel of aluminum oxide.

In my Patent 1,297,724; for silica gel and process of making the same Idisclosed and claimed a new method of producing hard porous highlyadsorbent gels. The specific example mentioned in the patent is silicagel.

Prior to my patent the only known way of producing gels employed theslow and impractical step of dialysis. This was a laboratory method andwould never have permitted the manufacture of gels in such quantitiesand cheap enough, so that they could be employed in the arts. My patentabove mentioned describes how to avoid this step and manufacture gelscheaply and quickly so that they can be utilized in many fields.

The present invention relates to another species of the inventiondisclosed in the patent. More specifically, it is directed to a methodof producing the gel of aluminum oxide either as such or in combinationwith one or more of the oxidesof titanium, tungsten or tin.

The principal object of the invention is to produce a gel of aluminumoxide either alone or combined with other colloidal oxides possessinggreat adsorbing powers, and by a method which is commerciallypracticable.

For the method of the present invention, 1 carefully determine theconcentrations of an acid solution and a solution of a soluble salt,such as a sodium saltvof the acid of aluminum oxide, such that whenmixed, will set to a hydrogel within four or five hours after mixing.Great care must be exercised in bringing the acid and salt solutionstogether, in order to avoid a rapid coagulation. To prevent thiscoagulation it is necessary to vigorously stir the solutions at themoment of mixing. The amounts of the salt solution and the acid solutionused are such as to give a final concentration of the H ions coming fromthe acid in the mixture varying between one-tenth and five-tenths molsper litre. The salt solution should be of a concentration of from 3% to7% by weight. Care should be taken to add the salt solution to the acidsolution, or to bring them together simultaneously. If the acid solutionis added to the salt solution the result will be a failure.

Thus for the production of aluminum oxide gel, a 3% to 7% solution ofsodium alummate is added to an acid solution, for example hydrochloricor sulphuric acids, unt1 l the concentration of the hydrogen ions comingfrom the acid in the mixture is from one-tenth to five-tenths mols perlitre, andpreferably about one-tenth to two-tenths mols per litre. Thesodium aluminate and. acid solutions are thoroughly stirred at the timeof mixing to prevent premature coagulation. The mixture sets to ahydrogel 1n a short time and is then broken into pieces and moistureremoved as directed hereinafter.

The temperature of the solutions during the time of mixing and settingis an important factor in the time required for the setting of thehydrogel. At a temperature of about 50 C. the mixture sets to a'hydrogel in thirty minutes to one hour and the prodnot is just as goodas the gel formed by mixlng the solutions at a lower temperature butrequiring a considerably longer time to set. Usually solutions at thetime of mixing and at the time of setting are at atmospherictemperaturebut satisfactory results may be obtained at temperatures from15 C. to 80 C. On mixing the acid and the soluble salt solutions, aeolloidal'solution of the acid corresponding to the oxide is firstformed. It is from this solution that the compound sets to a hydrogel.The hydrogel which is formed by allowing the mixture to set is thenbroken into pieces and washed free from acid and salt. If the wash wateris heated this step is expedited. The washed hydrogel must now have itsmoisture removed to obtain the hard gel. When this is effected bydrying, it is essential that the water he removed slowly, as theresulting finely porous condition of the gel obtained depends upon theproper drying of the hydrogel. To this end the hydrogel is first driedin a stream of air at 7 5 C. to 120 C. After this heating the gel willstill contain a considerable quantity of water and the greater part ofthis is driven off by increasing the temperature slowly up to 300 C. to400 C. It may, however, be dried at 120 C. but this will take longer. Ina general way lt may be said that not all the water should be driven outof the gel.

The resulting product is a most stable substance which can be safelyheated to relative- -ly high temperatures such as 700 C. Without fear ofinjury. The method of drying may be modified by taking the materialafter the first heating step as above described, and subjectin the sameto a vacuum to further remove the water, the temperature durmg thisvacuum treatment being from 75 C. to 120 C. The product obtained by thismethod' is just as stable as if the water had been mensions. It isbecause of this fine porous structure that the gel is such an eflicientad sorbing medium. The hardness which the and a solution of an acid,

gel possesses is a desirable property for the reason that the gel willretain its shape and structure and not crumble or pack when placed in avessel for the purpose of adsorbmg fluids.

In the foregoing description it was stated that a solution of thesodium-salt of the acid corresponding to the oxide is employed. It is tobe understood, however, that any solubl'e salt of the acid correspondingto the oxide may be employed. The gel prepared in accordance with thisinvention, in addition to being an efiicient adsorbent of fluids, alsopossesses marked catalytic activity.

By mixing solutions of a soluble salt of the acid of aluminum oxide andsoluble salt of the acid of one or more of the oxides of titanium,tungsten or tin, a gel will be obtained which may be termed a pluraloxide gel. The concentrations and quantities of the solutions aredetermined as already described, and the hydrogel formed by the mixturemay have its moisture removed by drying as previously set forth. In thismanner plural gels of any number of combinations of said oxides may beobtained. For example a plural gel of aluminum oxide and tungstic oxidemay be obtained by mixing with vigorous stirring 3% to 7% solutions byweight of sodium aluminate and sodium tungstate for example hydrochloricuntil the hydrogen ions in the mixture have a concentration of one-tenthto five-tenths mols per litre. Then the mixture is allowed to set to ahydrogel, broken into pieces and dried as described herein.

Having thus described the invention what is claimed as new and desiredto be secured by Letters Patent is:

1. In the process of preparing aluminum oxide gel, the step of addingwith thorough stirring a 3% to 7 solution of a soluble 3. The process ofaluminate to an acid solution, the amounts of the aluminate and acidsolutions and the stirring a soluble aluminatesolution to an acidsolution, the amounts and concentrations of said solutionsbeing suchthat the final concentration of H ions resulting from the acid inthe-mixture is from one-tenth to five-tenths mols per litre.

preparing aluminum oxide gel consisting inadding w1th thorough stirringa soluble aluminate solution to an acid solution, said solutions beingof such concentrations and amounts that the final concentration of Hions resulting from the acid in the mixture is from onetenth' tofive-tenths mols per litre, whereupon after a time the mixture will setto a hydrogel without removal of any of the excess acid and salt,thereafter washing said hydrogel to re .move the acid and salt, andremoving most of the water from the resulting product.

4. The process of preparing aluminum oxidegel consisting in adding withthorough stirring 8.3% to 7% solution of sodium aluminate to a solutionof an acid, the concen tration of the acid and the amounts of thesolutions being such that the final concentration of H ions resultingfrom the acid in the mixture is from one-tenth to five-tenths mols perlitre, whereupon the mixture, after a time, sets to a hydrogel withoutremoval of any of the excess acid and salt, washing the hydrogel toremove acid and salt, and removing most of the water from the resultingproduct. I Y

5. The process of preparing aluminum oxide gel consisting in addlng withthorough stirring soluble aluminate solution to an acid solution,saidsolutions being of such amounts and concentrations that the finalconcentration of H ions resulting from the acid'in the mixture is fromone-tenth to five-tenths mols per litre whereupon, after atime, the mixture sets to a hydrogel washing said hydrogel to remove acid an salt,drying the hydrogel at a temperature of to 120 C. to drive off a part ofthe moisture and then slowly increasing the temperature to drive pfl?the greater part of the remaining moisure.

6. The process of preparing a plural oxide gel containing aluminum oxideconsisting in adding with thorough stirring solutions of a solublealuminate and soluble salts of the oxides to an acid solution,

acids of the other the solutions being of such concentrations andamounts that the final concentration of H ions resulting from the acidin the mixture is from one-tenth to five-tenths mols per litre,whereupon, after a time, the mixture will set to a hydrogelwithout-removal of any of the excess acid and salts, washing to removeacid and salts and drying to remove most of the water from the resultingproduct.

7. A plural oxide gel being a hard glassy material havingultra-microscopic pores, stable in the presence of air up to hightemperatures, and consisting of aluminum oxide and one or more colloidaloxides.

8. In the process of preparing aluminum oxide gel, the steps of allowinga colloidal solution of aluminic acid to set to a hydrogel, drying thehydrogel in a current of air heated to 75 C. to 120 C. and then slowlyincreasing the temperature.

9. In the process of preparing aluminum oxide gel, the steps of allowinga colloidal solution of aluminic acid to set to a hydrogel, drying thehydrogel in a current of air heated .to 75 to 120 C. and then slowlyin-' creasing the temperature to 300 to 400 C.

10. In the process of preparing aluminum oxide el the steps of allowinga colloidal aluminlc acid solution to set to a hydrogel, dryin thehydrogel in a current of air heate to 75 to 120 C. and then slowlyincreasing the temperature to a point not exceeding 400 C.

11. In the process of preparing aluminum oxide gel, the steps ofallowing a colloidal solution of aluminic acid to set to a hydrogel,drying the hydrogel in a current of air heated to 75 to 120 0.,subjecting the gel to a vacuum and then further heating the gel.

12. The process of preparing a plural oxide gel containing aluminumoxide consisting in adding with thorough stirring 3% to 7% solutions ofa soluble illuminate and soluble salts of the acids of the other oxidesto an acid solution, the solutions being of such concentrations andamounts that the final concentration of H ions resulting from the acidin the mixture is from one-tenth to five-tenths mols per litre,whereupon, after a time, the mixture will set to a hydrogel Withoutremoval of any of the excess acid and salts, washing to remove acid andsalts and drying to remove most of the water from the resulting product.

In testimony whereof I hereunto affix my slgnature.

l/VALTER A. PATRICK.

